User blog comment:Funsizedbear/Generation 5/6 theory (mostly just a mod)/@comment-32077647-20180529135710

Aura trio:

Zygarde: Order

Xerneas: Life

Yveltal: Destruction

The trio balances life and destruction,Zygarde,the order pokemon mostly balances life and death (Hayds) While Xerneas fully controls life and Yveltal fully controls DEATH.

Tao Trio:

Reshiram: Vast white

Zekrom: Deep black

Kyurem: Boundary

Reshiram represents the concept of yang and controls Fire, Zekrom represents the concept of yin and controls Thunder, and Kyurem represents the concept of wuji (the absence of yin and yang) and controls Ice; in its alternate forms it can also control Reshiram's fire and Zekrom's thunder to some extent. (Google)